Washington DC - President Joe Biden denied Monday that Israel's war on Gaza was genocide, as he slammed what he called an "outrageous" request by the International Criminal Court's prosecutor for an arrest warrant for Israeli leaders.

"What's happening is not genocide," Biden told a Jewish American Heritage Month event at the White House.

His remarks referred specifically to a case at a different tribunal, the UN International Court of Justice (ICJ), which is dealing with allegations by South Africa that Israel's war on Gaza is genocidal.

But he also amped up his criticism of the ICC, a separate war crimes court, saying that "we reject" ICC Prosecutor Karim Khan's bid to arrest Israel's Prime Minister Benjamin Netanyahu and its defense minister.

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Khan also sought the arrest of top Hamas figures, including the Palestinian militant group's leader in Gaza, Yahya Sinwar, and political chief Ismail Haniyeh.

"Whatever these warrants may imply, there is no equivalence between Israel and Hamas," Biden told the audience in the Rose Garden of the White House.

Biden pledged "ironclad" support for Israel, adding that "we stand with Israel to take out Sinwar and the rest of the butchers of Hamas."

The US president further vowed to free hostages taken by Hamas during the October 7 attack "come hell or high water."

Hours earlier, he had issued a written statement saying that the ICC warrants were "outrageous."

Biden's expression of support comes despite recent tensions over Israel's war in Gaza. Washington recently withheld a shipment of bombs to Israel in a bid to warn it off an offensive in the southern city of Rafah, though it has continued to provide billions of dollars' worth of weapons to the Israeli state.

US Secretary of State Antony Blinken warned separately that the ICC prosecutor's move "could jeopardize" ceasefire talks to end the Gaza conflict.

"We reject the prosecutor's equivalence of Israel with Hamas. It is shameful," Blinken said in a statement.

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US lawmakers were reportedly considering a legislative response punishing the ICC amid bipartisan fury among Republicans and Democrats.

Republican House Speaker Mike Johnson slammed the court's "baseless and illegitimate" decision. He accused Biden of a "pressure campaign" against Israel, claiming the country was "fighting a just war for survival."

Biden faces political pressure on both sides ahead of a November election clash with Donald Trump, with pro-Gaza student protests rocking US campuses while Republicans accuse him of failing to fully back Israel.

The White House refused to comment on whether the US could take retaliatory action, including sanctions, against the ICC if it targeted Israel.

In 2020, the administration of then-president Donald Trump targeted the ICC with sanctions over its investigation in Afghanistan, but the Biden administration later lifted them.

Washington's ambiguous position over the court is reflected in the fact that it has backed the ICC's attempt to prosecute Russian President Vladimir Putin over the invasion of Ukraine.

Defense Secretary Lloyd Austin said Monday that the United States "will continue" to assist the ICC in its investigation into alleged war crimes in Ukraine, despite denouncing the Israel move.